A non-volatile memory device includes isolation layers, a cell trench, a floating gate, a common source region and a word line. The isolation layers define an active region of a substrate. The cell trench is formed in the active region. The cell trench extends in a first direction. The floating gate is formed on the active region and in the cell trench. The common source region is formed on the active region adjacent a second side face of the floating gate and extends in a second direction substantially perpendicular to the first direction. The word line is formed on the active region, which is adjacent to a first side face of the floating gate opposite to the second side face, and the isolation layers and in the cell trench. The word line extends in the second direction.